I agree with dt. I think Michael brought back Tom because he was not a bad consigliere. After Vito's death it was his choice. At the funeral Michael says having him not around when during the planning of the massacre was a luxury that he could not afford any more. And Tom survived in the movies and the book (yes I know he is dead by GF3 but it was because of the actor). I think Michael would have killed him in an instant if he had doubts about how he worked.
It was never filmed so it's meaningless, but the original Part III script where Tom Hagen is featured in it shows Michael and Tom working together again, and even goes further to show Tom's loyalty and love for Michael when Michael is killed at the end.
If Puzo and FFC never intended to play out the tensions between Mike and Tom in their original III script then I think all the "Mike hates Tom" stuff from I and II was just character flourishes to show how ruthless and conniving that Michael was when he wanted something.
I also believe that we as obsessive fans have looked into things a lot more than they should be looked into. As great a film as these movies are and as chess-like as some of the frictions are between characters, I think way more gets milked out of them than Puzo and FFC intended.
